This dataset contains the inside centroid point layer for the annually released statistical area 1 (SA1) boundaries as at 1 January 2021.The "inside" centroid is a point which always falls inside each SA1 polygon as this is often desirable. The placement of the point is typically in the widest part of the polygon. The algorithms used are proprietary to ESRI and are related to label placement. Note that the "inside" centroid is NOT always the same as the center of gravity ("true" centroid) of the polygon as in some situations the true centroid may fall outside the SA1 geometry. The dataset contains the EASTING and NORTHING attributes of the centroid point in NZGD2000 New Zealand Transverse Mercator (EPSG:2193) and LATITUDE and LONGITUDE of the centroid point in decimal degrees in WGS1984 (EPSG:4326) projection.
SA1s are based on the meshblock pattern. Non-alignment of meshblock to cadastral boundaries is one of a number of reasons for meshblock boundary adjustments. Other reasons include requests from local authorities, Local Government Commission, Electoral Representation Commission, and to make census enumeration processes easier. From the meshblock pattern, higher geographies, including the 2021 SA1 pattern, were dissolved using the dissolve tool in the Arc GIS suite. To derive the SA1 boundaries clipped to the coastline, meshblock polygons were dissolved to exclude meshblocks with a land/water attribute of Inlet or Oceanic.
Creative Commons Attribution 4.0 International (CC BY 4.0)